September 10, 2008

Neanderthals grew fast, matured later (?)

I haven't read this paper, but it's difficult to see how any statistically meaningful inference about the Neanderthal population can be derived from one neonate and two infants. Not only is the sample small, but after all it represents Neanderthals who died at an early age. Perhaps their mothers weren't large or nurturing enough to care for them...

Neanderthal brain size at birth provides insights into the evolution of human life history

Marcia S. Ponce de León et al.

Abstract

From birth to adulthood, the human brain expands by a factor of 3.3, compared with 2.5 in chimpanzees [DeSilva J and Lesnik J (2006) Chimpanzee neonatal brain size: Implications for brain growth in Homo erectus. J Hum Evol 51: 207–212]. How the required extra amount of human brain growth is achieved and what its implications are for human life history and cognitive development are still a matter of debate. Likewise, because comparative fossil evidence is scarce, when and how the modern human pattern of brain growth arose during evolution is largely unknown. Virtual reconstructions of a Neanderthal neonate from Mezmaiskaya Cave (Russia) and of two Neanderthal infant skeletons from Dederiyeh Cave (Syria) now provide new comparative insights: Neanderthal brain size at birth was similar to that in recent Homo sapiens and most likely subject to similar obstetric constraints. Neanderthal brain growth rates during early infancy were higher, however. This pattern of growth resulted in larger adult brain sizes but not in earlier completion of brain growth. Because large brains growing at high rates require large, late-maturing, mothers [Leigh SR and Blomquist GE (2007) in Campbell CJ et al. Primates in perspective; pp 396–407], it is likely that Neanderthal life history was similarly slow, or even slower-paced, than in recent H. sapiens.

2 comments:

Maybe you're right. But the Neandertal sample of fossils, though larger than most other fossilhumans, is still relatively small. They did have the fortunate, for us, habit of burying their dead, which is one reason so relatively many of them have been preserved. The upshot of all this is, that people who are trying to infer things about Neandertals, whether it be growth rates or anything else, have to work with whatever they can get.Anne G

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